<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<style>
			* {
				box-sizing: border-box;
			}
			.parent {
				border: 5px solid #000;
				/* 声明弹性容器 */
				display: flex;
			}
			.son {
				border: 5px solid #f00;
				/* width: 0px; */
				/* flex-basis: auto; */
				flex-basis: 0px;
			}
		</style>
	</head>
	<body>
		<div class="parent">
			<div class="son">11111</div>
		</div>
	</body>
</html>
